Self-controlled arc stream in gaseous discharge lamps

ABSTRACT

A discharge lamp with minimized upward bowing of the arc in which conductors carrying full arc current are placed in close proximity above and below the arc tube. The conductors run parallel with the longitudinal axis of the arc tube and the conductor (or conductors) above the arc are electrically connected in such a manner as to carry full lamp current in the same direction of the arc (thus repelling the arc in a downward direction) and the conductors below the arc tube are electrically connected so as to carry full lamp current in the opposite direction of the arc (thus attaching the arc downward).

United States Patent Kearney i 1 SELF-CONTROLLED ARC STREAM IN GASEOUSDISCHARGE LAMPS [75] Inventor: Joseph P. Kearney, Teuneck, NJ.

[731 Westinghouse Electric Corporation,

Pittsburgh, Pa.

Sept. 16, 1974 Assignee:

US. Cl. .1 313/154; 313/25; 313/161 Int. Cl. H01] 17/14 Field of Search313/156, 161, 184, 25,

References Cited UNITED STATES PATENTS 3,562,583 2/1971 Zollweg cl a1.313/161 X Primary E.rurnirwr-Palmer C. Demeo Attorney, Agent, or Firm-R.A, Stoltz [57] ABSTRACT A discharge lamp with minimized upward bowing ofthe arc in which conductors carrying full arc current are placed inclose proximity above and below the arc tube. The conductors runparallel with the longitudinal axis of the arc tube and the conductor(or conductors) above the are are electrically connected in such amanner as to carry full lamp current in the same di rection of the are(thus repelling the arc in a down ward direction) and the conductorsbelow the arc tube are electrically connected so as to carry full lumpcurrent in the opposite direction of the are (thus attaching the arcdownward).

4 Claims, 1 Drawing Figure 18 r 36 M I /2 F; 40 r 2 f l .l. I 1LSELF-CONTROLLED ARC STREAM IN GASEOUS DISCHARGE LAMPS BACKGROUND OF THEINVENTION The present invention relates to controlling the arc bowingnormally encountered in arc discharge lamps. When a discharge lamp isoperated with the arc-tube in a position other than essentiallyvertical, and in particu lar when the arc tube (and arc) are in ahorizontal or near horizontal position, the arc discharge does notremain along the central axis of the arc tube during continuedoperation, but bows upward within the arc tube. This are bowing can andoften does result in early lamp failure through excessive heating of aparticular portion of the arc tube wall.

It is well known that in high pressure mercury vapor lamps operated athigh power levels in a horizontal burning position, such lamps tend tohave a hot portion of the arc tube. Electro-magnetic means have beenused to deflect the arc-discharge down into a more central portionwithin the arc tube by directing the magnetic field transverse to thearc current direction wherein the inner-action of the arc dischargecurrent and magnetic field results in a downward force on the arc.

US. Pat. No. 3,562,583, issued to Zollweg and Burnham on Feb. 9, I971describes a magnetically rotating, constricted arc discharge devicehaving electromagnetic means to rotate a resultant magnetic fluxgenerally transverse to the arc discharge to cause the arc discharge torotate about the longitudinal axis of the arc tube and thereby avoiddestructive arc bowing.

The use of a separate electromagnet consumes extra power, takes up agreat deal of space, and can block a large amount of the light emittedfrom the arc tube. Permanent magnets can also be used, but they also arebulky and generally block a significant amount of light.

SUMMARY OF THE INVENTION The instant invention provides an inexpensivetech nique for stabilization of the arc ofa gaseous discharge lampwithout drawing current in addition to lamp current or blocking asubstantial amount of light.

The invention is (in combination with a discharge lamp of the typewherein an elongated arc tube having a main electrode in either end,between which electrodes an arc is established during operation, andwhich arc tube is contained within a light transmitting outer envelope)the improvement which comprises; at least three refractory metalconductors located inside of the outer envelope and outside and in closeproximity to the arc tube, which conductors run generally parallel tothe longitudinal axis of the arc tube and are electrically connected inseries with the main electrodes. The conductors are electricallyconnected such that when the lamp is operated with the arc other thansubstantially vertical, at least one of the conductors is generallyabove the arc tube and is carrying full arc current in the samedirection as the arc and at least two of the conductors are generallybelow the arc tube and are carrying full arc current in the oppositedirection of the arc. The magnetic effect from the current in both theconductors above the arc tube and the conductors below the are tubetends to counteract the natural upward bowing of the arc.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of theinvention, reference may be had to the exemplary embodiment shown in theaccompanying drawing in which:

The sole FIGURE is a side elevational view of a discharge lampconstructed in accordance with the pres ent invention, with parts of theouter envelope broken away.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the sole FIGURE there isshown the general arrangement of a high pressure mercury vapor dischargelamp within which refractory metal conductors in close proximity to thearc tube are used to stabilize the arc. The lamp, generally designated10, includes an outer light transmitting envelope 12 which is sealed toa mogul base 14. Other types of bases such as a mogul bipost may also beused, as it should be noted that proper orientation of the refractorymetal conductors (ie having the conductor which carries current in thesame direction as the arcs located above) is essential to properoperation. Mounted within the outer envelope l2, and spaced therefrom,is an arc tube 16. The are tube I6 is mounted within the outer envelope[2 by a two-piece frame, comprising a base-end frame 18 and a dome-endframe 20. Sealed within the arc tube 16 and disposed at opposite endsthereof are a pair of main electrodes 22 and 24. The base-end mainelectrode 22 and the dome-end main electrode 24 are sealed through theends of the arc tube 16 by conventional ribbon seals 26. A startingelectrode 28 is also sealed to the arc tube adjacent to base-end mainelectrode 24 by means of a ribbon seal 26.

A pair of lead-in conductors 30 extend through a conventional reentrantstem press 32 connected to the mogul base 14, which in turn is connectedto a conventional power source through a ballast 34 in the well knownmanner.

A starting resistor 36 is connected between one of the lead-inconductors 30 and the starting electrode 28.

A top refractory metal conductor 38 is positioned above the arc tube 16.Bottom refractory metal con ductors 40 are positioned below the arc tube16. One end of the top conductor 38 is electrically connected to the oneof the lead-in conductors 30 and the other end of the top conductor 38is electrically connected to one end of one of the bottom conductors 40.The other end of that same bottom conductor 40 is electrically connectedto the base-end main electrode 22. The other bottom conductor 40 iselectrically connected on one end to the other lead-in conductor 30 andon the other end to the dome-end main electrode 24.

It will be noted that some lamps of the prior art have used two-pieceframes 18, 20 as shown in the Figure while others have used one-pieceframes. Typically, when one-piece frames are used, the current to thedome-end main electrode is carried through the frame. The instantinvention can be used with either one-or two-piece frames, but thetwo-piece frame, as shown in the FIGURE, is preferred.

Phosphor coatings are commonly used on the interior surface of the outerenvelope of high pressure discharge lamps, and, if desired, can be usedin conjunction with the instant invention. Except for the refractorymeta] conductors 38, 40 used in the instant invention to counteract thearc bowing, the lamp operation is essentially conventional. Adescription of the config uration and operation of a conventional highpressure discharge lamp may he found in US. Pat. No.

Eff-183d} issued to ihorington on May I IJ'So.

The in tant invention permits a gaseous discharge light source tooperate in the borivontal mode more el ficiently and more safely sinceit minimi/cs the natural bowing of the arc stream, which bowing normallycauses the are to come into very close proximity of the wall of the aretuhe l6 (and sometime actually touching it). When using this invention,the arc stream is more centrally located keeping a more uniformtemperature and more of the light producing materials in a vapor state.resulting in better efficacy. The more central location of the arcprevents violent failure which can he caused by the arc stream comingvery close to or actually touching the arc tube 16. Although theimention is intended for use primarily when the are tube 16 is operatedin other than a vertical manner, the invention also assists instahilizing the are when the arc is vertical.

To provide substantial stabilization. it has heen found that therefractory metal conductors 38 and 40 must he in close proximity to thearc tuhe. (icncrally the con ductors must be within a quarter of an inchand prefer ably within it i s of an inch ofthe arc tuhe substantiallythroughout the entire arc length. These conductors 38, 4t! should he asclose as practical to the arc tube l6 and can actually touch the arctube 16. Because of the tenr per-attire on or near the arc tube 16 beingquite high, it is necessary to use a refractory metal for suchconductors. In order to minimize the light blocked by the conductors 38,40 it is also desirable that they be of small diameter lrihhonconductors can also be used and should be positioned with their largercross sectional dimension in radial relationship with the are such thatthey proiide a minimum shadowing of the light emitted by the arc].

The refractory metal conductors 38, 4!) are connected in seriesrelationship with each other and in serics relationship with the arccurrent. This can he :chieied in a number of manners. For example, onelcadin conductor 30 can he connected directly to the base-end mainelectrode 22. lhe other lead-in conductor 30 is then run under the aretube 16 and past (but not connected tot the dome-end main electrode 24.back above the are tuhe 16 past (but not connected to} the hase-end mainelectrode 22 and then under the arc tube to back to and connected to thedome-end main electrode 24 (in this configuration the three conductors38. 40 can he formed by a single piece of wire).

Another alternatiie {the alternatiie shown in the FIGURE! is to run arefractory metal conductor 40 from one of the leadin conductorsunderneath the arc tuhe l6 and connect it to the domc-end main electrode24. Refractory metal conductor 38 is run from the other lead-inconductor 30 above the arc tuhe l6 past lhut not connected to) thedome-end main electrode 24 and then run (as refractory metal conductor40) under the arc tube 16 back to and connected to the base-end mainelectrode 2. This configuration has the advantage that the refractorymetal conductors 38, 40 can be conveniently supported by a singleadditional support tat the point at which the conductor is going past,but not connected to. the dome-end main elec trode 24).

Ill

(it t Such lamps are generally run on ac current and the direction ofthe current reverses every half cycle both in the are, and in therefractory metal conductors 38, 4t), During both halves of the cycle,the current in the top refractory metal conductor 38 is in the samedirection as the arc current and therefore always repels the aredownward. The currents in the bottom refractory metal conductors 40 arealways opposite the are current and therefore are always tending to pullthe arc downward.

Configurations in which more than three conductors are used willfunction in the mode of the invention although it will he noted that theuse of more conductors tends to block more of the light emitted from thearc tube. It can be seen that a five refractory metal conductorconfiguration in which there are two top conductors 38 and three bottomconductors 40 can be electrically connected in a manner similar to theaforementioned three refractory metal examples. The two top conduo tors38 and three bottom conductor 40 configuration can he produced by, forexample, connecting the baseend rnain electrode 22 directly to one ofthe lead-in conductors 3t) and running a piece of refractory metal wire[which will form the five refractory metal conductors) from the otherlead-in conductor 30 under the arc tube In, past the dome end electrode24, above the arc tube 16 back past the haseend electrode 22, under thearc tube 16 past the domeaend eiectrode 24. above the are tube 16 pastthe base-end electrode 22, and under the arc tube 16 and connecting tothe domeend main electrode 24. [t can be seen that even more fie seven)refractory metal conductors can he used in a similar manner.

While lamps can he fabricated with a single refrac tory metal conductorclose to and below the are tuhe. experiments have shown that such aconfiguration is unsatisfactory as it does not provide adequate controlof arc bowing.

The instant invention can he used with high pressure mercury lamps andwith halide lamps (it should be noted however that sodium containinglamps when used with the instant invention will generally experienceincreased photo-electric problems due to the close proximity of theconductors to the arc tube 5. The instant invention provides a cheaperand more convenient configuration than units in which magnets are used.

l claim.

1. In combination with a discharge lamp of the type wherein an elongatedarc tube having a main electrode in either end, between which electrodesan arc is cstablished during operation, and which are tube is containedwithin a light transn'iitting outer envelope, the improvement whichcomprises:

at least three refractory .rnetui conductors located inside of saidouter emelope, and outside and in close proximity to said are tube andrunning generally parallel to the longitudinal axis of said are tube,said conductors being electrically connected in series with said mainelectrodes and being electrically connected such that when said lamp isoperated with said are other than substantially vertical, at least. oneof said conductors is generally above said are tube and is carryingcurrent in the same direction as said arc, and at least two of saidconductors are generally below said are tube and carrying eur rent inthe opposite direction as said are, whereby the magnetic effect from thecurrent in both the cunduetur ahuve the arc tube and the euntluetorsbelow the are luhe tends to counteract the natural upward bowing of thearc.

2. lhe lamp of claim I. wherein three refractory is tungsten metalcumlucturs are used.

1. In combination with a discharge lamp of the type wherein an elongatedarc tube having a main electrode in either end, between which electrodesan arc is established during operation, and which arc tube is containedwithin a light transmitting outer envelope, the improvement whichcomprises: at least three refractory metal conductors located inside ofsaid outer envelope, and outside and in close proximity to said arc tubeand running generally parallel to the longitudinal axis of said arctube, said conductors being electrically connected in series with saidmain electrodes and being electrically connected such that when saidlamp is operated with said arc other than substantially vertical, atleast one of said conductors is generally above said arc tube and iscarrying current in the same direction as said arc, and at least two ofsaid conductors are generally below said arc tube and carrying currentin the opposite direction as said arc, whereby the magnetic effect fromthe current in both the conductor above the arc tube and the conductorsbelow the arc tube tends to counteract the natural upward bowing of thearc.
 2. The lamp of claim 1, wherein three refractory metal conductorsare used.
 3. The lamp of claim 1, wherein said refractory metal isselected from the group consisting of tantalum, tungsten, andmolybdenum.
 4. The lamp of claim 3, wherein said refractory metal istungsten.